Rack mounted power supplies are well known and are widely used for supplying DC power to nearby devices. For example, 19″ and 9.5″ racks are very widely used. Each of such power supplies is in fact a unit which is designed to supply voltage and current, in levels as specified by the user. Each power supply unit generally comprises an AC to DC stage, a DC to DC converter (which is fed, for example, from a Pulse Width Modulation-PWM circuitry), and a controller for regulating the output levels of the power supply and for managing the entire operation of the unit. Typically, each unit is composed of several substantially identical power modules, all of which are regulated and controlled by said single controller.
Although reference is made herein to rack mounted power supplies, this should not be viewed as a limitation, as the invention is applicable also to power supplies that are not rack mounted.
Typically, each power supply may operate in a constant-voltage (CV) mode which is the most common operational mode, or in a constant-current (CC) mode (in which the output acts as a current source).
Each of such power supply units is also typically designed to operate either as a stand-alone entity, or in a combination with other similar units. More specifically, when a necessity arises for a supply of more power than can be supplied by a single unit, several of such units are commonly connected in parallel.
The prior art has provided a configuration for connecting plurality of power supply units in parallel. In such a configuration, a first power supply unit is defined as “master”, while each of the additional units is defined as “slave”. The output ports (positive and negative) of all the units are respectively joined in parallel such that the combined configuration results in a single output pair, while each of the units contributes its own current to the load. In this configuration, the master unit is set to a specific output voltage level (and sometimes also a limitation to the current level is set), while it also generates a “monitor” output signal which is fed to each of the slave units. This “monitor” signal, in fact, reflects the level of current that the master unit supplies to the load, while each of the slave units uses this signal to regulate its own output current to match said level of the master unit current. In such a manner, all the slave units in fact operate in a current-feedback (current follower) mode, while the master unit operates in a voltage-feedback mode.
The above master-slave configuration in which the master unit operates in a voltage feedback mode, while all the slaves operate in a current-follower mode (current feedback that enforces the current of the slave unit to “follow” the current level of the master unit) suffers from a significant drawback: The slave units follow the output of the master unit in a very slow manner—for example, in transient events in which a fast and significant change in the current consumption occurs, the master unit operating in a voltage-feedback mode reacts to this change in a fast manner, while each of the slave units reacts in a much slower manner, which affects the performance of the entire system. For example, upon a fast increase in the current consumption from the system, the output voltage may initially decrease and then relatively slowly return to its specified output voltage. On the other hand, in the master unit this process occurs very fast. A similar problem occurs during soft adjustment of the master unit voltage and current levels by the user. In both of said cases the imbalance in the performance between the master and the slave units significantly affects the dynamic performance of the entire combined system, which in fact does not react to transients like a single unit operating alone.
In still another aspect, the configuration of the prior art master-slave system is quite cumbersome, as it requires the user to provide both soft configuration definition (such as defining the “master” and “slave units” via a UI or the front panel), and a hard-wire configuration, namely connecting multiple wires at the back panels.
It is therefore an object of the present invention to provide a master-slave power-supply system which reacts to dynamic transient consumption in a much faster manner compared to similar prior art master-slave systems.
It is another object of the present invention to provide a system in which the power consumption from the various units and modules is much more balanced compared to the prior art.
It is still another object of the present invention to provide a master-slave power supply system which is homogenous, operating like a single unit.
It is still another object of the present invention to provide a master-slave power supply system which is scalable to include any number of slave units.
It is still another object of the present invention to provide a master-slave power supply system which can be configured in a fast and simple manner, with no need for user setup via a user interface.
Other objects and advantages of the present invention will become apparent as the description proceeds.